RedDog382

The threads on one of the bolt holes for the inspection covers of my Stellings extension boxes is stripped out. I am considering using a Helicoil to repair it, but the aluminum is very porous and seems to flake very easily. I am afraid the Helicoil may not hold given the consistency of the metal.

Has anyone else had this problem or have any other suggestions for a fix?

Reed Jensen

If you are afraid of using a heli-coil...and if you find the right industrial supply store.. you can get an insert... it works almost the same way as a heli-coil..You drill out the stripped threads and rethread the hole, except the insert has a "wall" rather than just what appears to be wire threads... but you have to have enough casting to accomodate the thicker insert... there are advantages to inserts over heli-coils... they use standard taps, and can be coated with lock-tite.
I'd suggest trying the heli-coil first... then if it strips out... go to the insert.

RedDog382

R.J.,

Thanks for the suggestion. Sounds like that may be the ticket if the Heli-coil fails.

Audiofn

I think that what read is talking about is called a TIME SERT or TINE SERT or something like that....

They do work well but I believe are cast not stainless like a helicoil is. They may make them out of stainless but I have never seen one (of course I have never looked either....) You can grab any grainger, McMaster, or MSD Machine catalog and find hundreds of different kinds.


Jon

Reed Jensen

There are different names for them... what you may be talking about is a nut-sert... or a riv-nut... Riv-nuts are like a hollow threaded pop rivet.. only larger diameter.. they are more common to sheet metal construction.. but you can spec them with flat heads for countersunk applications.. and they can also be used on thick metal if you get the correct ones and they are available in different metals.. including stainless.... Threaded inserts look more like a grub screw that has been drilled out and threaded.

Cord

iTrader: (2)

I have the tools and the inserts for these little fellows. Maybe I'm not using them correctly, but I havn't had much luck with them in thick material applications. The heli-coil is going to be your best bet. Very carefully drill the hole with the correct sized bit. Make sure you go slow and keep it cool. You must have a accurate hole. Now lube that tap up real well. Remove the tap often and clean the chips off before they can gall. If you mess up these threads you'll be screwed. The only other option will be to go up to a 5/16" thread or weld and redrill the hole.

I know how hard it can be to get the cover screws started. Are you using allen screws? If not, I'd recommend switching to them. I use a T handle wrench which makes the installtion easier. You can see when the screw is not threaded in straight and you have enough leverage to actually twist the screw into alignment.

WAGS382

RedDog,
Don't you have a friend in mentor who is a tool and die maker? The above mentioned insert is available in stainless, if you let me know what size thread you are repairing I will get the part number and where to get it. Jeff the tool and die maker

mcollinstn

Keenserts and Timeserts are available in stainless.
In high vibration applications, the timeserts work well. Helicoils are NOT good to use in applications where vibration and potential creeping is present.

The best option is a GH3 (standard nominal) tap for the insert, used with heavy tapping oil in a properly sized pilot hole (drill 1/64 undersize before finishing with the correct tap drill). Then clean the thread with lacquer thinner and install the stainless insert with green (bearing retainer grade) Loctite. Permanent repair. End of story.

Reed Jensen

Hmmmm.... if they aren't good for high vibration applications... then why do original aircraft parts have them installed ?......... I've seen turbine housings from GE that have them installed....

RedDog382

Guys,

Thanks for all your responses and suggestions! I like to tinker with mechanical stuff, but I'm not a professional so I wanted to solicit a few expert opinions before I really screwed something up!



Jeff,

How about a little off-season get together for some minor repairs? (And don't try to convince me that I need to replace these Stellings boxes with new ones so you can put them on your 382! )

Chris